Alloy



Patented June 23, 1931 UNITED STA RICHARD R. WALTER, OF STARNIBERG, GERMANY ALLOY No Drawing. Application filed. September 20, 1929, Serial No. 394,137, and in Germany December 3, 1928.

M invention pertains to alloys and more particularly to alloys characterized by great reslstance to wear and furthermore adapted to use on tools for cutting.

Articles composed of tungsten carbide especially suited for use upon tools and implements have hitherto been manufactured by melting and casting. Tungsten carbides, like more or less all of the metals solidified from melted state, show especially enhanced crystal. tension which manifest themselves by the brittleness and hence rapid nonuseability of the tools. However, since sintered metals or alloys are uniformly distinguished by freedom from tension the tungsten carhides have come to formation and manufacture in this manner. But in order not to have to heat them to the softening point or far over two thousand degrees centigrade (2000 C.) it was proposed to add thereto, before sintering, lower melting temperature. metals are therefore purposed to cause the individual powder particles of the tungsten carbide to stick together or to become fused to each other.

Preformed .pieces manufactured in that nlilanner have a considerable firmness so that t e ple to chip-lifting tools like, lathe tools, milling cutters, drills, reamers, in the art of say metal working. The object of this practice is the attainment of substantially better cutting performances and consequently the tools 5 are subjectedto conslderabledemands as regards their mechanical firmness or cohesive tenacity. Since the tungsten carbides manifest a considerable resistance to wear as well as great hardness, it becomes evident that the auxiliary metals which bind the carblde particles together must not be permitted to lessen the desideratum and that one cannot use every conceivable low-melting metal for th1s pur ose. 4

T e requirements, mechanical strength coupled for instance with the cuttmg tips of tools of tungsten carbide, include a thermalresistance adaptability because the tips frequently glow red at the customary cutting aside of the necessary metal powders of markedly Such auxiliary.

are suitable for application, for exammentioned, which are speeds. Under that condition-the adhesive auxiliary metals should neither reduce the mechanical strength nor the resistance to wear.

It follows as a matter of course that a series of-heretofore suggested auxiliary metals,

for instance iron, must be declared to be use- I less because of loss of hardness and softening when glowing red. Cobalt for example, has also been proposed as an auxiliary metal, but this metal has not yet produced satisfactory results and the cutters of tungsten carbide sintered with the aid of cobalt are known to be very prone to fracture.

Contrary to previous knowledge, this invention primarily utilizes even metals of high melting temperature, indeed, from the chromium group and together with them metals of the iron group. Owing to the presence of metals of the chromium group, as for example tungsten or chromium or both, together with for instance cobalt the auxiliary metals employed according to this invention attain a Stellite-similar character and it is known that such retain their natural hardness at temperatures approaching one thousand degrees C.

(1000 C.) in addition to their extraordinary resistance to wear. Even the use of only tungsten and cobalt produces auxiliary metals of mechanical strength and heat-resistant-quality superior to that of cobalt by itself.

Yet while in the case of employment of hitherto adopted auxiliary metals their amount could not' exceed twenty per cent (20%) if the alloys were not to'beeome useless, it is now established that the auxiliary metals according to my invention can be added in considerably greater amounts than hitherto with the result that cutting strength becomes improved and the brittleness and hence the fracturing of the cutting inlays becomes lessened. This result is illuminating from the circumstance that the auxiliary a great metals of Stellite-like character pursuant to does not produce any more improvement in the qualifications.

It was further discovered that tungsten carbide can be replaced by azotized tungsten carbide or tungsten carbonitride (W C -Nx) or the two mixed together with good result. These .complex compounds display a substantial increase in mechanical strength as against'even the hardest carbides and their resistance to Wear likewise exceeds that of the pure carbides. a A The nitrification isfacilitated and possible even with the metal tungsten if efiected subsequent to or simultaneous with acarburization, either while glowing in pulverized carbon or in the presence of heat through transit-ion of hydrocarbons and while exposed to dissociated nitrogen.

The majority of the metals of the iron and chromium group's, singly or a plurality together, may be utilized as auxiliary metal and azotized carbides or carbonitrides of the metals of these groups may also be advantageously employed. As is known, a slight addition of boron can increase the hardness when desired. The manufacture of the alloys is achieved in the ordinary way by compression of the powdered ingredients and by sintering in a nonoxydizing atmosphere.

The following compositions are formulae exemplifications of alloys comprehending this invention: seventy-eight (7 8%) per cent. azotized tungsten carbid t, (W. UN.) 5 eleven (11%) per cent. cobalt; eleven (11%) per cent. tungsten;.and: sixty-seven (6'Z%) per cent. tungsten carbide (WU) five (5%) per cent. tungsten 'carbonitride (2 WCl/S W N eighteen (18%) per cent. tungsten (W) eight (8%) per cent. cobalt (Co) 5 two (2%) percent. chromium carbide (Cr C I claim i 1. An alloy comprising a powdered, mixed, compressed and sintered'n etallic aggregate, comprising over fifty per cent of a carbonitride of metal of the chromium group. and up to thirty per cent of a high melting metal of the chromium group and as remainder metal of the iron group.

2. An alloy comprising powdered, mixed, compressed and sintered aggregate of tungsten carbonitride andqauxiliary metal comprising at least fifty per cent of tungsten carbonitride and from five-to a maximum of thirty per. cent of high melting auxiliary metal of the chromium group with'metal of the iron group as remainder. I

An alloy comprising apowdered, mixed, compressed and sintered metallic aggregate comprising a major portion of a carbonitride of metal of the chromium group and a minor portion of an auxiliary metal of the iron group and together with a metal of the chromium group of higher melting temperature than the metal of the iron group.

4. Analloy comprising a powdered, mixed,

compressed and sintered metallic aggregate comprising a major proportion of an azotized tungsten carbide, an auxiliary metal of the Signed by me, this 10th day of August, 1929.

RICHARD R. WALTER. 

